Individuals with mental retardation (MR) experience an exceptionally high prevalence of health related problems. The incidence of obesity for people with MR is higher than the general population and is recognized as a major health problem. For overweight persons weight management is recommended; for individuals with MR this recommendation is critical. In the 1980s, effective weight management programs were developed for people with MR that took advantage of the best existent behavioral technology. Since then, there have been no additional developments in weight management for this population despite a compelling need. Due to the passage of time, these weight management programs from the 1980s are out of print. This project will use the best of the behavioral programs specifically designed for individuals with MR while incorporating recent advances in weight management. The primary aims of the study are developing, implementing, and evaluating the efficacy of a weight loss/maintenance program among obese adults with MR with effective strategies for improving nutrition by changing eating behaviors, increasing physical activity, involving parents as learning partners, and practicing weight-maintenance activities. To accomplish these aims we will develop a comprehensive individualized, weight-loss intervention and evaluate its effectiveness in a randomized field study (to be completed in Phase n). In Phase I, we will develop the initial sessions of the intervention and conduct a pilot study to determine skill acquisition and user acceptance. Innovative aspects of the proposed program include the strong emphasis on weight maintenance and the active involvement of a learning partner (parent). The program will be designed to not only teach specific weight loss/maintenance techniques to the individual with MR, but also to educate and motivate the learning partner to become actively involved in their family member's weight loss program and subsequent maintenance efforts. Research on obesity, due to its implication with cancer, heart disease, diabetes and a host of other disorders, is highly relevant to public health. The NIH Obesity Research Task Force has listed prevention and treatment of obesity through lifestyle modification as one of four major goals that need to be pursued by the public health community. By focusing on individuals with mental retardation, this program brings needed intervention tools for an underserved, high-risk population.